Carbon nanotubes (CNT) have been the subject of intense research since their discovery in 1991. CNTs possess unique properties such as small size, considerable stiffness, and electrical conductivity, which makes them suitable for a wide range of applications, including use as nanocomposites, molecular electronics, and field emission displays. Carbon nanotubes may be either multi-walled (MWNTs) or single-walled (SWNTs), and have diameters on the nanometer scale.
Depending on their atomic structure CNTs may have either metallic or semiconducting properties. These properties, in combination with their small dimensions, make CNTs particularly attractive for use in the fabrication of nano-devices. A major obstacle to such efforts has been the difficulty manipulating the nanotubes. Aggregation is particularly problematic because the highly polarized, smooth-sided fullerene tubes readily form parallel bundles or ropes with a large van der Waals binding energy. This bundling perturbs the electronic structure of the tubes, and it confounds all attempts to separate the tubes by size or type or to use them as individual macromolecular species. Various methods have been used to disperse carbon nanotubes. For example, commonly owned U.S. Patent Appl. 20040132072 and WO 2004/048256, teach that nucleic acid molecules are able to singly disperse high concentrations of bundled carbon nanotubes in an aqueous solution.
Sol-gel techniques to prepare inorganic, crystalline materials, especially metal oxides, are very well-known in the art. Dispersing carbon nanotubes in such a matrix can produce materials with many valuable properties, such as enhanced conductivity and improved strength.
Vincent, P. et al., (J. of Non-Crystalline Solids 311 (2002), pg. 130-137) and Ning, J., et al., (Ceramics Internat. 30 (2004) pg. 63-67) both prepared composites of multi-walled CNTs in a metal oxide sol-gel matrix. However, although multiwalled CNTs are easier to manipulate than single-walled CNTs, homogenous dispersion was not achieved.
Dong, W., et al., (Science and Tech, of Adv. Materials 4 (2003), pg. 3-11) prepared vanadium oxide aerogels using suspensions of SWNT's, however significant agglomeration was seen.
There is a need therefore for conductive materials comprising single walled carbon nanotubes for use in nanodevices. Applicants have met that need through the discovery that inorganic metal oxides can be formed containing a highly dispersed network of single walled carbon nanotubes, producing novel materials with unique properties.